Backup of a SQL Server may fail with a VSS error.

From the log, the following message can be found:

One or more errors occurred. ---> Replay.Core.Contracts.Transfer.VssGeneralErrorException: There was a problem with the VSS subsystem on '(agent-machine)l'. ---> Replay.Agent.Contracts.ShadowCopy.ShadowCopyWriterFailedException: The VSS writer 'SqlServerWriter' failed during the 'DoSnapshotSet' phase with error WriterErrorNonRetryable. The VSS writer state is FailedAtPrepareSnapshot ---> Replay.Common.Contracts.ReplayException

In the Application event log on the machine, event 8229 is logged:

Event 8229

A VSS writer has rejected an event with error 0x800423f4, The writer experienced a non-transient error. If the backup process is retried, the error is likely to reoccur.

The problem is most likely due to insufficient access for the SQL Server VSS writer to write to the VSS shadow copy, because the service is not running as an Administrator account, but rather as the Local System account.

1. Open Windows Services (services.msc).
2. Open the properties of the service SQL Server VSS Writer.
3. On the Log On tab, change the "Log on as:" to "This account" and fill in the account name and password of a local administrator account. It can also be a domain administrator or a regular AD account with local administrator rights).
4. Click OK to save the changes. Right-click the service and restart it for the changes to take effect.

From the Rapid Recovery console, take a new snapshot. The backup should now complete without errors.